Remove dependency on PrefChangeRegistrar and renderer_preferences_util from content.

content/browser/renderer_host/render_view_host_observer.h

Index: content/browser/renderer_host/render_view_host_observer.h
===================================================================
--- content/browser/renderer_host/render_view_host_observer.h	(revision 86641)
+++ content/browser/renderer_host/render_view_host_observer.h	(working copy)
@@ -8,6 +8,7 @@
 #include "ipc/ipc_channel.h"
 
 class RenderViewHost;
+struct ViewMsg_Navigate_Params;
 
 // An observer API implemented by classes which want to filter IPC messages from
 // RenderViewHost.
@@ -28,6 +29,9 @@
   // chance to cleanup.  The base implementation will delete the object.
   virtual void RenderViewHostDestroyed();
 
+  // Notifies that a navigation is starting.
+  virtual void Navigate(const ViewMsg_Navigate_Params& params);
+
   // IPC::Channel::Listener implementation.
   virtual bool OnMessageReceived(const IPC::Message& message);